There’s been a flare-up of a very contagious canine influenza in the metro area.

That includes Long Island, northern New Jersey, Connecticut and the lower Hudson Valley, said Dr. Edward Dubovi, director of the virology section at Cornell University’s Animal Diagnostic Center.

“It’s unclear whether there are cases currently in the city proper,” he said.

Canine flu “starts out as an upper respiratory infection,” he said. “If you think of the common cold in people, you have the same type of issue with dogs.”

“In uncomplicated situations, it does not appear to be serious,” Dubovi said, explaining that your dog might have a low-grade fever or runny nose, stop eating or develop a cough.

“It could go away, but it could morph into something serious, and there’s no way of looking at your dog and saying, ‘Oh, it’ll be OK,’ ” Dubovi said.

An example of a serious complication would be a secondary bacterial pneumonia, which if not treated could prove fatal, he said.

Better be safe than sorry, vets say. There is a vaccine available to protect dogs, who often catch the flu in close quarters, such as doggy day care or kennels.

Dr. Yasmine Mortsakis, the veterinarian at Biscuits & Bath, a chain that offers doggy day spas, overnight boarding, grooming and vet care at six Manhattan locations, says they’re urging clients to get the vaccine.

“We haven’t seen any cases, but I expect pretty soon we will be, unfortunately,” she said.

The flu is “not transmissable to people,” she said.

Biscuits & Bath charges $45 for the vaccine, and the same for a follow-up booster if the dog has not been previously vaccinated.

The North Shore Animal League, which says it has seen no cases of canine flu, offers the shots for $35 each.

“If you bring a dog to a dog park where there is communal activity, it’s good to have the dog vaccinated,” said league spokeswoman Devera Lynn.

The city Health Department said yesterday that “there is no current evidence of an outbreak” of canine flu at the city’s Animal Care and Control shelters.

In New Jersey, the Bergen County animal shelter in Teterboro shut for about two weeks last month because some dogs came down with the flu.

All of the affected dogs have since recovered, have been given their flu shots and are available for adoption, the shelter said in an Oct. 27 posting.